This invention relates generally to electronic testing equipment and more particularly circuit boards used for interfacing a plurality of test points in such equipment.
With the increase in test point density test equipment, manufacturers have introduced in-circuit testers that interface with seven thousand and more test points. With an average test nail spring pressure of 5.5 oz., the force over a given area can reach 2400 pounds. Of course, this force is distributed over an area determined by the product being tested and the number of test points. In-circuit test fixturing has evolved over the years, from wired fixturing using 26-30 gauge wires to xe2x80x9cwirelessxe2x80x9d test fixturing which uses double ended spring pins and a circuit board to carry any given signal, instead of conventional wiring. Hence, the problem arises of a high density, high force test area flexing the circuit board of a wireless fixture with concomitant continuity and contact problems.
To make certain testers upgradeable and compatible with previous versions, a modification has been designed to add additional test points to a tester and allow earlier xe2x80x9cwiredxe2x80x9d test fixtures to be used. This was accomplished by lowering the location of additional test points. From an interfacing standpoint on a conventional wired test fixture, the conversion was simple. Lower the wirewrap pins to the lower level and continue wiring.
However, high density test points, such as seven thousand and more wires, become a debugging problem. Further, induction problems associated with this many wires in such close proximity to one another becomes problematic.
Wireless test fixturing has been an answer to this problem. Since the average length from product under test to the interface is 2xe2x80x3 vs 18xe2x80x3 of 28 gauge wire, the multilevel interface becomes a problem with circuit board design and manufacturing. The designs presently being utilized have failed due to intermittent contact to a flex interface printed circuit board and failed solder joints where the connector that transfers the signal to the lower portion of the interface meets with the interface printed circuit board.
It is an object of the present invention to overcome the limitations of the prior art noted above.
Additional objects and features of the invention will be set forth in part in the description which follows and in part will be obvious from the description. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
Briefly, in accordance with the invention, a lower portion of the interface circuit board is fabricated in unison, i.e., integrally, with the signal portion of the routed signal portion as a single piece which not only strengthens the interface board but also allows for signals to pass through the multithickness board without solder joint failures. The routed signal is passed through the transfer portion through a blind via and then to a test pad where the interface circuit board is connected/interfaced to the testing equipment.